Cal Fire firefighters wait for a helicopter to pick them up up on the outskirts of Mount Diablo State Park in Clayton, Calif., on Tuesday, Aug. 24, 2010. (Ray Chavez/Staff) ** MAGS OUT/MANDATORY CREDIT **

Photo: Ray Chavez, AP

Cal Fire firefighters wait for a helicopter to pick them up up on...

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The Curry Fire on the east slopes of Mt. Diablo State Park was reported at 80 percent containment on Wednesday morning.

Photo: Michael Macor, The Chronicle

The Curry Fire on the east slopes of Mt. Diablo State Park was...

Image 3 of 3

The Curry Fire on the east slopes of Mt. Diablo State Park was reported at 80 percent containment on Wednesday morning.

"It's down to the really rugged canyons where it's just smoldering now," Streck said. "There are no active flames and just a little bit of smoke. The worst is behind us."

The blaze was reported at 4 p.m. Tuesday near Curry Canyon and Morgan Territory roads about 6 miles southeast of Clayton. The cause is under investigation.

Helped by hot, dry weather, the fire crackled through thick brush and oak woodlands toward a ridge near Mount Diablo. Some structures were initially threatened, but firefighters were able to save them. There were no evacuations.

The lack of wind overnight kept the fire from spreading, while some 300 firefighters worked in shifts beating back the flames and setting up a perimeter.

Three helicopters dropped water and fire retardant and 120 firefighters struggled to build a firebreak Wednesday in the canyon where the last embers were burning. Streck said he expects full containment today.

Two firefighters were treated for sprained ankles and a third cut his leg.